The present invention relates to a method and a device for operating a clutch between an internal combustion engine and at least one driven wheel of a vehicle, a torque being transmitted between the engine and the driven wheel by pressing the clutch together, using a clamping force or a clamping load.
If a clutch is operated with slip, then conclusions can be drawn regarding the transmitted clutch torque, when the friction coefficient of the clutch lining is known. This torque information shall be utilized for determining the input torque of the transmission. An exact measurement of the transmission input torque is especially important in continuously variable automatic transmissions (CVT), in order that the safety pressure in controlling the belt tension of continuously variable transmissions can be reduced, and the transmission efficiency can be increased.
The object of the present invention is to improve the operation of a clutch.
The object is achieved by a method and a device for operating a clutch between an engine and at least one driven wheel of a vehicle, while operating clutch situated between an engine and at least one driven wheel of a vehicle; by pressing the clutch together with a clamping force or a clamping load, a torque being transmitted between the engine and the driven wheel, the clamping force or clamping load being adjusted as a function of an engine torque generated by the engine, and as a function of the inaccuracy of the information about the torque generated by the engine, or as a function of the speed of the engine, and, in particular, certain speed ranges being assigned a specific degree of inaccuracy of the information about the engine torque generated by the engine. In this context, inaccuracy is to be understood as, for example, the standard deviation or a multiple of the standard deviation.
In an advantageous refinement of the present invention, the clamping force or the clamping load is ascertained as a function of a clutch slip in the clutch, while the torque is transmitted between the engine and the driven wheel.
In an advantageous further refinement of the present invention, the clamping force or the clamping load is set as a function of the torque transmitted by the clutch.
In another advantageous refinement of the present invention, the torque transmitted by the clutch is ascertained as a function of the clutch slip in the clutch, while the torque is transmitted between the engine and the driven wheel.
In another advantageous refinement of the present invention, the clamping force or the clamping load is adjusted as a function of the friction coefficient of the clutch.
In another advantageous refinement of the present invention, the coefficient of friction of the clutch is ascertained as a function of the clutch slip in the clutch, while the torque is transmitted between the engine and the driven wheel.
In another advantageous refinement of the present invention, the correlation between the torque transmitted by the clutch and the clutch slip, or the correlation between the friction coefficient of the clutch and the clutch slip, are adapted when the (known) inaccuracy of the information about the engine torque is less than or equal to a first tolerance value.
In a further advantageous refinement of the present invention, the adaptation is carried out as a function of the clamping force or the clamping load.
Another advantageous refinement carries out the adaptation as a function of the difference between the clutch slip and a setpoint value for the clutch slip.
In another advantageous refinement of the present invention, the clamping force or the clamping load is controlled by an automatic controller, as a function of the difference between the clutch slip and a setpoint value for the clutch slip.
In a further advantageous refinement of the present invention, the adaptation is carried out as a function of the engine torque.
In an additional advantageous refinement of the present invention, the coefficient of friction xcexc of the clutch is corrected according to   μ  =      μ    +                            T          M                ·        i                                          T            M                    ·          i                +                  T          R                    
where
TM≅i is the input torque introduced into the clutch by the engine, taking into consideration transmission ratio i of a transmission between the engine and the clutch; and
TR is a differential torque output by the controller.
In a further advantageous refinement of the present invention, the information about the engine torque generated by the engine is corrected, when the (known) inaccuracy of the information about the engine torque is greater than a second tolerance value.
In an advantageous refinement of the present invention, the information about the engine torque generated by the engine is corrected as a function of the difference between the clutch slip and the setpoint value for the clutch slip.
In another advantageous refinement of the present invention, the information about the engine torque generated by the engine is corrected according to       T    MK    =            T      M        +                  T        R            i      
where
TM is the engine torque;
TMK is the corrected engine torque;
TR is a differential torque output by the controller; and
i is the transmission ratio of a transmission disposed between the engine and the clutch.
In another advantageous refinement of the present invention, the first tolerance value is equal to the second tolerance value.
A particularly advantageous refinement of the present invention provides for the clutch having a clutch lining, and the clutch lining being selected to have a certain friction-coefficient characteristic. This improves the adjustability of the clutch. In particular, the intention here is that, in the range of small clutch-slip values, the friction coefficient of the clutch increase more sharply with increasing clutch slip, than in the range of larger values of clutch slip.